Scuba-diving mouthpieces of various kinds have been known and used for many years. The great majority of such mouthpieces are not customizable for individual divers, but some customizable scuba-diving mouthpieces have been known or used. Examples of customized or customizable scuba-diving mouthpieces are those shown in U.S. Pat. Nos. 3,107,667 (Moore), 3,844,281 (Shamlian), 3,929,548 (Shamlian), 4,136,689 (Shamlian), 5,031,611 (Moles) and 5,305,741 (Moles).
Despite advances in recent years, there are many problems and shortcomings with scuba-diving mouthpieces of the prior art, including those of the above-listed patents. One fairly common problem relates to mouth fatigue experienced by scuba divers including those of the above labeled patents.
The Moles patents identified above brought about significant improvements that helped to overcome many of the problems related to mouth fatigue and the production of a customized fit. Despite such significant improvements, problems still remain particularly in regard to the lack of a tight seal between the mouthpiece and the diver's gums and the gag reflex that results when an object is inserted in the rear portions of the mouth.
Regarding the formation of a tight seal, mouthpieces of the prior art are unable to form as strong a seal between the diver's gums and the mouthpiece itself as may be desired. Known mouthpieces are shaped such that the top and bottom of their front portion are substantially aligned with the diver's gum line. Such alignment prevents the formation of a strong seal between the diver's gums and the mouthpiece thereby allowing for water to seep into the diver's mouth. A mouthpiece that would more comfortably allow for the formation of a seal between itself and the diver's gums would be an improvement in the art.
Another major problem associated with scuba-diving mouthpieces is the gag-reflex that is activated by the extension of the bite portion further back into the diver's mouth. While moving the contact location between the diver's teeth and the mouthpiece further back in the mouth decreases jaw fatigue, such extension increases the likelihood that the diver will "gag" on rear portions of the mouthpiece. There is a need for improvements which will serve to decreasing jaw fatigue while reducing the propensity for gag-reflexes.
Finally, the outer surfaces of known scuba-diving mouth-pieces are such that the diver's lips and cheeks are forced to stretch in order to completely surround the device. An improvement in the shape of the outer surface such that it would allow the diver's mouth to close more naturally around the mouthpiece would be an important improvement in the art.
Mouthpieces are typically held in place by means of the diver's bite on retaining members which project inwardly from a lip-engaging portion to positions between the upper and lower teeth. This not only places significant pressures on small portions of the diver's teeth, that is, the portions engaging the retaining members, but the constant muscle pressure needed for secure retention of such mouthpieces can cause significant muscle strain and aching.
The problems of jaw fatigue and joint strain during long use are accompanied by a related problem--a tendency toward an inability by the diver to easily maintain the mouthpiece in the proper orientation, particularly when pressures are applied to the mouthpiece from outside the diver's mouth. Unwanted pressures on the mouthpiece grip come from water currents (relative to the diver), contacts made with diving apparatus, and a variety of other causes. It is essential, of course, that the diver's mouthpiece, which is the sole source of air, remain in place. Thus, the concern about pressure interfering with the grip of the diver on his or her mouthpiece is more than a casual concern.
Some problems with current scuba-diver mouthpieces can be understood better by reference to the mouth, the jaw, and the teeth of a typical person. The jawbone is a lengthy angled member which pivots with respect to the skull and about the jaw joint well back from the mouth. Such joint is typically positioned considerably above the level of the teeth and well behind the position of the teeth. From such joint, the jaw has a generally downwardly and slightly forwardly extending portion which extends generally to a position rearwardly spaced from the teeth, and a more forwardly, but still downwardly, extending portion which carries the teeth of the lower jaw and extends forwardly beneath the upper jaw. The angle between the two positions of the lower jaw is referred to herein as the "jaw angle."
Opening and closing muscle tissue masses are secured to the jaw at positions forward of the jaw joint, but well rearward of the teeth. The muscles secured to the lower jaw create a lever arm which extends from the jaw joint all the way to the point of contact pressure of the lower jaw with the upper jaw or with whatever is being bitten.
When using a typical diving mouthpiece, or a customized diving mouthpiece such as those shown in the aforementioned Shamlian patents, the lever arm of the lower jaw extends from the jaw joint all the way forward to the position of the eye teeth where the mouthpieces are gripped between the diver's teeth.
Two separate problems are created when the mouthpiece contact occurs in this manner at such forward position in the mouth: First, since the distance from the center of muscle effort is long, a significant increase in muscle force is necessary to stabilize and retain the mouthpiece. This is what causes the muscles to quickly fatigue and often to become painful, which leads to jaw aches and headaches. A second and related problem of such long lever arm is created when standard mouthpieces, or customized mouthpieces of the Shamlian type are used, in that there is a severe increase in pressure within the jaw joint, well back in the head.
If the contact location is extended to the back of the mouth, the lever arm is shortened and advantages are achieved, including a reduction in the muscle force necessary to hold the mouthpiece and a reduction in the corresponding jaw pressure. Lengthening the mouthpiece retention piece to allow contact at a more rearward position in the mouth creates a shorter, and thus more favorable, lever arm. This resists torque from movement of the diver's regulator. That is, a better grip can be maintained with less exertion.
However, extension of the posterior bite pieces has been difficult or unworkable in the prior art due to variability in the jaw alignment of different people. Only a completely customized bite portion would allow for this. The variability in the angle between the teeth of the upper and lower jaws is a major problem. Such variability is caused by variations in the aforementioned lower jaw angle and also by the angle of the upper jaw with respect to the lower jaw. The upper jaw may be tipped up or down in the front or back.
Furthermore, the extension of the bite pieces result in an increase of the gag-reflex. Therefore, in order to take advantage of the reduction in jaw fatigue that results from a reduction in the length of the lever arm, alterations must be made to the bite portions in order to reduce the possibility of gagging.
While there have been a number of efforts to make improved customizable scuba-diving mouthpieces, there has remained a clear need for significant improvements in the field of customizable scuba-diving mouthpieces.